Cable Modem Research Articles

An overview of reliable multicast transport protocol II

This document provides an overview of the reliable multicast transport protocol II, RMTP-II. RMTP-II is a reliable multicast protocol, designed to reliably and efficiently send data from a few senders to large groups of simultaneous recipients. It works over both symmetric networks and asymmetrical network topologies such as those provided by satellite, cable modem, or ADSL carriers. Before sending, each sender must connect with a trusted top node to receive permission and control parameters for its data stream. The top node provides network managers with a single point of control for the senders, allowing them to monitor and control the traffic being sent. RMTP-II builds on a rich field of existing work, and adds to it the following novel contributions. It differentiates the roles of the nodes in the protocol, provides algorithms for smoothing and control of the return (TRACK) traffic, and provides explicit support for highly asymmetrical networks. It provides explicit network management controls through a centralized point of control, a fully distributed membership protocol that enables positive confirmation of data delivery, and fault recovery algorithms which are integrated to the reliability semantics of the protocol. It includes a novel reliability level called time bounded reliability, and offers a unique combination of TRACKs, NACKs, and FEC for increased scalability and real-time performance. Finally, it integrates distributed algorithms for RTT calculation to each receiver, and provides automatic configuration of receiver nodes.

The broadband revolution

The broadband revolution truly is of the same magnitude as the industrial revolution of the 1800s. The changes we're going to see over the next decade will principally come from the connected home. We'll see bandwidth increasing a thousandfold from today's voice band 56-Kbps modems to tens of megabits per second through DSL and cable modems, and other satellite and wireless technologies. To have an impact on the millions of people who do not have computers, we'll need to turn the television set into a medium that somewhat simulates what they would now get with a computer and add fully interactive video at broadband speeds. The future connected home will have numerous service providers sending a broad pipe to the home over satellite, cable, DSL, or terrestrial wireless. It doesn't matter how we connect the home; we'll see a broadband gateway in the home, much like today's office that has a broadband router connected to the Internet. The connected environment doesn't necessarily have to be wired, but cable and phone lines are a natural choice, especially in the US, and will be first to market with the widest deployment. There will be no rewiring; clearly if we have to rewire, we'll never have a market. We'll also need wireless mobile connectivity within the home for all the devices we'll use. The telephones will be converted to Internet videophones, and MPEG video will be delivered over the Internet. As we are well aware, the TV set is being upgraded substantially. Certainly the HDTV format with the 16 x 9 aspect ratio and high resolution display will finally allow us to read Web pages on the TV set in a reasonable format. We'll have fancy on-screen displays and videophone pop-up screens with a TV camera sitting on the TV set so we can make video calls to Grandma.

HomeRF: wireless networking for the connected home

The SWAP specification for wireless voice and data networking within the home will enable a new class of mobile consumer devices that draw from the power and content of the Internet and the home PC. If cable modems and xDSL represent the "last mile" access to the home, then HomeRF/sup TM/'s mission with SWAP could be called the "very last 150 feet" within and around the home. HomeRF has the broad backing of the major corporate stakeholders for networking within the home and is optimized specifically for the cost/performance point needed for consumers. The technology leverages the existing PC-industry infrastructure around the Internet, TCP/IP, and Ethernet, and adds a standard way to connect to the PSTN for voice telephony. First products should appear in late 1999, and future versions with enhanced features and/or higher data rates should follow in one to two years.

A 3 V 10 b 100 MS/s digital-to-analog converter for cable modem applications

This paper describes a 10 b 100 MS/s CMOS digital-to-analog converter (DAC) for cable modem applications. Differential switches with the proposed deglitching circuit and the cascode current sources, separated from the unit decoded current cell matrix improve the dynamic performance. The proposed and conventional prototype DACs are fabricated in a 0.35-/spl mu/m CMOS process. The measured differential and integral nonlinearities of the proposed DAC shows /spl plusmn/0.17 LSB and /spl plusmn/0.43 LSB at a 10 b level, respectively. At 100 MS/s, the spurious-free dynamic range is 66 dB for a 100 kHz input signal and 52 dB for a 10 MHz input signal.

Effective competition in European telecommunications: an analysis of recent regulatory developments

Shows that some national governments’ policy to promote specific market structures have either proved ineffective (France) or increased entry barriers, likely to raise industry cost (Spain). Argues high‐speed cable modems are the way forward for the future. Concludes, in order to achieve long‐term efficiency, the regulator should promote a mix of infrastructure and service competition to enable viability in the long term.

Effective competition in European telecommunications: an analysis of recent regulatory developments

Shows that some national governments’ policy to promote specific market structures have either proved ineffective (France) or increased entry barriers, likely to raise industry cost (Spain). Argues high‐speed cable modems are the way forward for the future. Concludes, in order to achieve long‐term efficiency, the regulator should promote a mix of infrastructure and service competition to enable viability in the long term.

Availability of Broadband Internet Access: Empirical Evidence

Broadband access is needed for the Internet to achieve its full potential, and how these services are offered is likely to have important implications for the extent of competition for communication services in the last mile. This paper describes a research project of the MIT Internet & Telecoms Convergence Consortium (ITC) into local Internet access and presents initial results from our empirical survey of the patterns of deployment for broadband Internet access in the United States, focusing on xDSL and cable modems as the two technologies that have been deployed most extensively to date. We were unable to find much evidence of residential xDSL deployments through the end of 1998; however, we did identify over 805 communities where cable modem services are now available. The demographics of these communities suggest that to date that these services are still not widely available, and where available, are concentrated in higher income, higher density markets -- as might be expected for a new technology. Moreover, when broadband access is available, consumers are unlikely to face competitive alternatives for providers. And, finally, the identity of the cable television provider has had an important impact on the likelihood that cable modems will be available. We suspect this result reflects differences in strategic decisions based on differing views of the attractiveness of broadband services and earlier decisions on the timing and extent of system upgrades. For example, MediaOne has been substantially more aggressive in deploying cable modem services than have carriers with typically lower-quality outside plant, such as Cablevision and TCI. While these results are not surprising, they are nevertheless important in helping to establish a baseline for continued research and in suggesting additional data requirements and questions that need to be examined to more fully understand the evolution of Internet access. In addition to the empirical data presented, we describe our future research agenda.

Workload characterization of a Web proxy in a cable modem environment

This paper presents a detailed workload characterization study of a World-Wide Web proxy. Measurements from a proxy within an Internet Service Provider (ISP) environment were collected. This ISP allows clients to access the Web using high-speed cable modems rather than traditional dialup modems. By examining this site we are able to evaluate the effects that cable modems have on proxy workloads.This paper focuses on workload characteristics such as file type distribution, file size distribution, file referencing behaviour and turnover in the active set of files. We find that when presented with faster access speeds users are willing to download extremely large files. A widespread increase in the transfer of these large files would have a significant impact on the Web. This behaviour increases the importance of caching for ensuring the scalability of the Web.

Henry Samueli

With the explosion in the popularity of cable and digital subscriber line modems for high-speed Internet access, the odds are that there will be one of these broadband communications devices in many homes or offices. The odds are that the chips inside the modem will have been designed by Broadcom Corp., and be based on digital signal-processing (DSP) architectures conceived by Henry Samueli. The author presents a biography of Samueli from his school days through his work in the defense industry and his teaching career to the co-founding of, and work at, Broadcom.

TCP behavior over HFC cable modem access networks

Hybrid Fiber-Coax based CATV networks have the potential for two-way data services. Such network providers are presently re-inventing the CATV network to provide Internet access. This paper presents a simulation study of the dynamic behavior of TCP over HFC cable modem networks. We believe that this is the first such study as per our knowledge that considers asymmetry and its impact on TCP behavior. The performance of TCP connections with respect to flow control, adaptive retransmission mechanism and slow-start congestion control are studied and analyzed. In particular, we explain the dramatically different behavior and dynamics that are observed for TCP connections using interactive data (remote-login), bulk data (FTP) and Web traffic (HTTP). We further study and discuss the impact of several important TCP and system parameters to optimize performance in CATV networks.

A method to eliminate effect of phase noise in OFDM synchronization system

OFDM (the orthogonal frequency division multiplexing) and its variety DMT (the discrete multitone) as delegates of the multicarrier modulation technology have given a big impact on the conventional data communication applications. Based on the theoretic a analysis of the OFDM technology, the impact of phase noise that introduced by the bit and symbol timing mechanism is discussed. Then a pilot correction and the cyclic prefix protection method are put forwarded to deal with the problem. These methods have been used in our experimental OFDM cable modem system to cope with the impulse noise and narrow band interference in the HFC (hybrid fiber and coax) upstream channel.

Performance evaluation of HTTP/TCP on asymmetric networks

As the number of Internet users grows, new network technologies are emerging. Those include ADSL and cable modem, which essentially provide asymmetric bandwidth for uplink and downlink to the user's connection. In this paper, we investigate the behaviour of HTTP/TCP protocols on such asymmetric networks, and present the analytic results of the mean throughput of TCP. The transfer time of Web documents by HTTP over TCP is also derived. In the analysis, we consider newer HTTP/TCP protocols, HTTP/1.1 and TCP Vegas, in addition to HTTP/1.0 and TCP Tahoe. We then investigate the appropriate combination of HTTP and TCP protocols on the asymmetric network. The results show that the effect of HTTP/1.1 is quite small, but TCP Vegas can improve the performance in asymmetric networks if it is appropriately modified as in our proposal. Copyright © 1999 John Wiley & Sons, Ltd.

Using proxies to enhance TCP performance over hybrid fiber coaxial networks

Using cable modems that operate at several hundred times the speed of conventional telephone modems, many cable operators are beginning to offer World Wide Web access and other data services to residential subscribers. Initial experiences indicate that real-world hybrid fiber coaxial (HFC) networks are susceptible to a variety of radio-frequency impairments that significantly reduce the benefits of using high-speed cable modems. The effects of packet losses in the access network are particularly accentuated during subscriber accesses to remote servers on the Internet. The longer round-trip times in such accesses together with the high packet loss rate result in dramatic degradations in performance perceived by subscribers. This paper shows that by using proxy servers to handle all remote accesses from an HFC access network, the performance of remote accesses can be significantly enhanced even in cases when the proxy servers do not function as data caches. By handling packet losses that occur in the HFC network locally, at low latencies and without the remote server even being aware of the loss, a proxy server enables faster recovery from packet losses. Most importantly, since it controls data transmissions over the local HFC network, the proxy server's transmission control protocol (TCP) implementation can be optimized for the loss of characteristics of the HFC access network, enabling a significant increase in performance when the access network is lossy.

Cable: it's not just for TV

Hybrid fiber-coaxial-cable systems can download data from the Internet at up to 30 Mb/s while also carrying multiple telephone channels and broadcast radio and TV signals-both analog and digital. This paper concentrates on single-access technology-cable modems. The cable modem packs the Internet data in the form of 10BASE-T frames, which are fed over an Rj-45 connection to the Ethernet network interface card (NIC) in a computer. The phone connections at the cable modem are for Internet protocol (IP) telephony, which has yet to come to residences in a big way. The connection between a cable modem and the Internet is packet-switched and so the link is always active. The standards for cable modems are discussed as is the sending of digitised voice over a packetised system.

An efficient scheme for accommodating synchronous traffic in a cable-modem network while avoiding segmentation of asynchronous packets

Cable-modem (CM) technology is being developed to provide high-speed multimedia services to the subscribers’ homes over the existing hybrid-fiber-coax (HFC) infrastructure of cable TV networks. The article proposes an efficient scheme for combining asynchronous and synchronous traffic on the upstream channel of a CM network when segmentation of the asynchronous packets is to be avoided, e.g. because of cost considerations. The new scheme guarantees the synchronous sources the same quality of service provided by the FDDI timed token protocol. That is, a guaranteed average delay between consecutive transmissions, a guaranteed maximum delay between consecutive transmissions, and a guaranteed bandwidth on the upstream channel.

(FTTH) system providing broad-band data over cable modems along with analog and digital video

We demonstrate that by applying cable modem technology in a 1550-nm EDFA-based fiber-to-the-home (FTTH) system we can deliver broad-band data services along with analog and digital broadcast video. The data system shares 30-Mb/s downstream and 2.56-Mb/s upstream over 64 living units, while the broadcast video system provides 77 analog channels and /spl sim/1 Gb/s of digital video.

Bring home the Internet

In the good old days, the only two-way communications link with a residence was provided by the local telephone company (telco). But the growth of the Internet and the passing, in the United States, of the Telecommunications Act of 1996 have changed that tradition. Today, a competitive local exchange carrier can compete in the turf of the local telco, now called an incumbent local-exchange carrier. In addition, cable TV operators are allowed to offer telephony and Internet access services to their subscribers along with TV programs. The question of who will supply the 'last mile' pipe to the home could lead to some of the toughest fights the communications marketplace has ever seen. Winners will gain the revenues from supplying a cornucopia of phone, TV and Internet services. The paper discusses these issues as well as asymmetric digital subscriber line, cable modems, service billing, wireless connections, and power grid use for optical cable laying for communications.

Two-way broadband CATV-HFC networks: state-of-the-art and future trends

Cable modems allow two way digital data transmission between households and a central neighborhood server. In this overview we briefly describe some of the common characteristics of the Hybrid Fiber Coax (HFC) operation as presented by several standards bodies (both completed standards and works in progress). This includes a description and comparison of the media access control and physical layer operations of several competing proposals. Our desire is to give a concise but complete picture of the cable modem problem and the proposed solutions. References are provided for readers interested in further investigation.

Wireless broadband communications: some research activities in Singapore

Almost a decade ago, Singapore started crafting and implementing its IT2000 master plan to transform the city-state into an information-technology-based intelligent island. Since 1997, the main infrastructure of a high-speed ATM-based backbone network, called SingaporeONE, has been in place along with a host of commercial and governmental application service sites providing a plethora of online services. Because of its small size and extensive wired infrastructure, broadband access to homes and offices is currently provided via ADSL and cable modems. There is, however, interest in the use of wireless broadband communication technologies to access SingaporeONE, motivated primarily by its lower cost and faster deployment. In this article we describe some of our R&D activities motivated by the above interest to provide wireless broadband access to SingaporeONE. Specifically, we describe our study of LMDS, and the design and development of a wireless ATM LAN.

An Architecture for Building Scalable, Web-BasedManagement Services

We present the architecture of Marvel, a distributed computing environment for building scalable management services using intelligent agents and the world-wide web. Marvel is based on an information model that generates computed views of management information and a distributed computing model that makes these views available to a variety of client applications. Computed views consist of monitoring, control and event views of information collected from network elements and subsequently aggregated using a series of spatial and temporal filters. Marvel does not replace existing element management agents but rather builds on top of them a hierarchy of servers that generate computed views and present them to client applications in a number of formats, including Java-enriched web pages. It uses a distributed persistent store to reduce the cost associated with centralized network management systems and mobile agent technology to: (a) support thin clients by uploading the necessary code to access Marvel services; and (b) extend its functionality dynamically by downloading code that incorporates new objects and services. A prototype implementation in Java is presented together with results from its first application on a residential broadband access system using cable modems.